Fluid pressure operated digital display

ABSTRACT

A digital display device is disclosed for displaying increments of mechanical movement, which includes a movable piston member having an ordered series of numerals inscribed thereon along its longitudinable axis and disposed in a bore having a window adapted to register with individual numerals on the piston. The piston position in the bore is controlled by venting of fluid pressure on one end thereof which is normally applied to both the ends with this venting in turn controlled by registry between a series of ports on a movable control plate and a series of ports in the bore wall which have a vernier spacing relationship therebetween so that a slight incremental movement of the valve plate produces a much larger movement of the piston in the bore. When combined with a similar second piston and bore arrangement controlled by a simple porting control performed by the same control plate, a digital display of control plate incremental movement in units and tenths of units of these increments is provided.

United States Patent 1191 Esken 1 FLUID PRESSURE OPERATED DIGITAL DISPLAY [75] Inventor: Robert L. Esken, Clayton, Ohio [73] Assignee: The Bendix Corporation, Southfield,

Mich.

[22] Filed: Jan. 27, 1972 [21 Appl. No.: 221,365

5 2 vs. (:1. 235/201 FS, 91/1, 91/47, 91/48, 91/357,116/65 [51] Int. Cl. G06d H02 [58] Field'of Search 235/201; 33/1 D;

3 [56] References Cited UNITED STATES PATENTS 2,876,543 3/1959 Dzaack 33/1 D 3,305,171 2/1967 Phillips et al. 235/201 Primary Examiner-Richard B. Wilkinson Assistant Examiner-Lawrence R. Franklin Attorney-William S. Thompson and John R.

Benefiel 111 3,739,165 [451 June 12, 1973 [57] ABSTRACT A digital display device is disclosed for displaying increments of mechanical movement, which includes a movable piston member having an ordered series of numerals inscribed thereon along its longitudinable axis and disposed in a bore having a window adapted to register with individual numerals on the piston. The piston position in the bore is controlled by venting or fluid pressure'on one end thereof which is normally applied to both the ends with this venting in turn controlled by registry between a series of ports on a movable control plate and a series of ports in the bore wall which have a vernier spacing relationship therebetween so that a slight incremental movement of the valve plate produces a much larger movement of the piston in the bore. When combined with a similar second piston and bore arrangement controlled by a simple porting control performed by the same control plate, a digital display of control plate incremental movement in units and tenths of units of these increments is provided.

10 Claims, 8 Drawing Figures BACKGROUND OF THE INVENTION 1. Field of the Invention This invention concerns'digital displays, and more particularly fluid pressure operated digital displays of increments of mechanical movement.

2. Description of the Prior Art Digital readouts of various. measuring instruments such as pressure gages have certain advantages, including ease of reading and reduction of operator errors due to interpolation of scales inherent in non-digital or analog type instrument readouts and hence would be superior to analog readouts if such a display could be provided which was sufficiently accurate, not unduly expensive, did not result in an excessively cumbersome and complex instrument, and which would provide a sufficiently large range to accommodate the range of readings to be encountered.

Electronic digital displays provide most of these requirements where the instrument is electrically operated, but in the case of pure mechanical instruments such as bourdon tube pressure gages the cost and the complexity added thereby is such that so equipping these instruments is seldom justified.

Prior art mechanical digital displays have suffered from a lack of sufficient range and/or incremental resolution to be practical in many situations. These devices have been for the most part simple dipstick type readouts as typified by the arrangements shown in U.S. Pat. Nos. 3,491,945 and 3,305,171. Since the incremental movement to be measured exactly corresponds to that necessary for changing a digital readout by an increment, extremely cumbersome devices would result if the number of digital readouts were on the order of fifty or a hundred units.

Therefore, it is an object of the present invention to provide a compact mechanical digital display of increments of mechanical movement with. an extended range as compared with similar prior art devices.

SUMMARY OF THE INVENTION This and other objects which will become apparent upon a reading of the following specification and claims is accomplished by providing a piston slidable in a bore and having the digital numerals inscribed thereon. The piston position is controlled by a movable control plate, incremental movement of which is that which is to be displayed, this control plate having a series of ports formed therein having a vernier relationship with a series of ports in the bore wall. Registry of these ports controls the position of the piston by controlling venting of the volume above one end of the piston so that a much greater movement of the piston results from a given incremental movement of'the control plate.

By combining this arrangement with a similar second piston and bore arrangement controlled by a simple (rather than vernier) porting control, a digital display of incremental movements of the control plate in units and tenths of units of these increments is provided.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view in partial section of a display device according to the present invention.

FIG. 2 is a view of the section taken along the line 2--2 in FIG. 1.

FIG. 3 is an enlarged view taken in the direction of the arrows 3-3 in FIG. 2.

FIG. 4 is the same view as FIG. 3 with the valve plate in a shifted position.

FIG. 5 is the same view as FIG. 3 with the valve plate in a shifted position.

FIG. 6 is the same view as FIG. 3 with the valve plate in a shifted position.

FIG. 7 is a front elevational view in partial section of a second embodiment of the present invention.

FIG. 8 is a side elevational view of the embodiment of FIG. 7.

DETAILED DESCRIPTION In the following detailed description, specific embodiments will be described and certain terminology will be utilized for the sake of clarity, but it is to be understood that these are merely illustrative and the invention may be practiced in a variety of forms and embodiments.

Referring to the Drawings, and particularly FIGS. l6, a digital display device 10 is depicted in partial section.

The digital display device 10 includes a housing structure 12 having a reference point display window 14 extending across the front thereof, in which the digital readout is to be displayed.

The embodiment shown is contemplated for use with a back pressure air gaging circuit and a brief explanation at this point of the nature of these circuits will be helpful in understanding the usefulness of the configuration to be described. These circuits have the characteristics of a rather short gaging range since they rely on an interaction between an air jet and a workpiece as is well known in the gaging art. For example, a 500 amplification air gaging circuit would have a useful range of approximately 0.0060 inches. For typical applications of such a circuit, a resolution of 0.001 inches would be adequate. Therefore, digital readouts in increments of 0.000l inches over a range of .0060 inches would require individual digital readings, which is typical for these circuits.

For this reason, the first two numerals 16, 18 would be fixed zeros since the complete reading for this example would always include these.

The next two numeral positions are controlled by the arrangement according to the present invention.

This arrangement includes a control plate 20 which is drivingly connected to the output of the pressure transducer 22 which converts pressure readings into analogous mechanical movement so that the position of the control plate 20 is analogous to that of the pressure sensed in the circuit, which is in turn analogous to the dimensional variation being sensed.

The position of the control plate 20 in turn controls the position of a first and second movable element comprising a pair of pistons 24 and 26-slidably disposed in a pair of bores 28 and 30 respectively formed in the housing 12.

Piston,24 has a tail" portion 32 attached thereto having an ordered series of numerals inscribed thereon, while piston 26 has an ordered series of numerals from 0-9 inscribed directly thereon as shown.

By a porting arrangement to be described herein in detail, piston 24in response to incremental movements of control plate 20, moves with these same incremental movements, which are selected to be that necessary to bring the next numeral into position in registry with the window 14.

Piston 26, on the other hand by a porting arrangement, also to be described herein in detail in response to movement of the control plate 20 through this same increment moves in bore 30 a distance of times this increment, so that all the numerals inscribed thereon are successively displayed at subincrements of movement'equal to one-tenth thereof.

There is also provided an arrangement whereby after movement of the control plate through each increment, piston 26 returns to the position shown and again moves so as to successively display each numeral at window 14.

Thus it can be seen that piston 24 displays what can be thought of as the tens values while piston 26 displays the units values corresponding to movement of valve plate 20.

By referring to FIGS. 26, the porting arrangement which accomplishes this function can be explained and understood.

The opposite ends of each piston 24 and 26 are pressurized with a fluid such as air supplied under regulated pressure via passage means indicated schematically at 34.

FIG. 2 shows the connections to bore 30 only for purposes of clarity, but it is to be understood similar connections are provided for bore 28 for the same purpose.

A metering orifice is provided at 36 and 38 to limit pressurization behind lands 40 and 42 respectively under steady state conditions with a given bypass flow past the lands 40, 42 and venting to atmosphere through port 41 such that the net fluid force acting on the piston 26 is zero via inlets 44 and 46 respectively provided in the housing 12. Thus under steady state conditions and with the control plate 20 in the zero position, the position of the piston 26 will be stabilized in the position shown in FIG. 2 since gravity will cause it to move to the bottom of the bore 30.

Contrariwise, the restrictions (not shown) for piston 28 are selected such that at the given leakage flow rate across the lands 46, 48 and venting to atmosphere through port 45 (FIG. 4), the net fluid force is directed upwardly and of a sufficient magnitude to overcome gravity and it will assume the full upward position shown in FIG. 1 so that all zeros appear in the window As best seen in FIGS. 2 and 3, bore 30 has formed therein a first series of control elements which in this instance takes the form of a series of ports 50 juxtaposed to the control plate 20. Formed in the control plate 20 is a second series of control elements also taking the form ofa series of ports 52 along a line with the series of ports 50 formed in the bore 30. The spacing of the port series 50 and the port series 52 have a vernier" relationship to each other, that is, nine equally spaced ports 50 are positioned as shown with nine equally spaced ports 52 with this spacing one-ninth greater than the spacing of the ports 50. This relationship causes each port 50 to successively register with the port 52 to its right as viewed in FIG. 3 as the control plate 20 is moved to the left a distance equal to the distance between each port 50.

This phenomenon is analogous to the successive registration of graduations on juxtaposed vernier scales as is well known in the field of linear measurement.

As the first port 50 to the left moves into registry with its corresponding port 52, the fluid under pressure in the bore 30 above the land 42 is thereby vented so that the pressure therein is reduced, creating a pressure unbalance since pressure on land 40 remains the same, and causing the piston to move to the right to the position shown in FIG. 4 to close off the first of the ports 50 sufficiently so that the pressure above land 42 will again create an equilibrium of forces on the piston 26.

At this position, the numeral 1 is displayed in the window 14.

Upon further movement of the control plate 20 to the left as viewed in FIG. 4 the first of the ports 50 moves out of registry with its respective port 52, and the piston 26 is again unbalanced by venting of the bore 30 above the land 42, and it then moves to restrict the second of the ports 50 until equilibrium is again restored, at which time the numeral 2 appears in the window 14.

This registry shift occurs successively with successive movements of the control plate 20 until the ninth of the ports 50 is in registry with its respective port 52 and the piston 26 is in its extreme upper position with the numeral 9 appearing in the window 14.

Upon further movement of the control plate 20, the ninth of the ports 50 moves out of registry but no other port 50 moves into registry so that no venting of the bore 30 above land 42 occurs, full pressure equilibrium occurs on the piston 26, and gravity causes the piston 26 to drop to the bottom of the bore 30 so that the zero numeral again appears in the window 14.

From this description it can be understood that a movement of the control plate 20 through a range equal to the spacing between ports 52 results in a number of incremental movements equal to the base of the decimal system or ten incremental movements of the piston (including the return to zero) corresponding to 10 numeral changes, and that this incremental movement is greater by an order of magnitude in the decimal system or 10 times that of the valve plate 20 movement. For example, a port 52 spacing of 0.025 inches will provide a numeral change of one unit for each 0.025 inches of control plate movement. This represents a great spacing saving in digital display over the prior art displays described.

In addition, this arrangement allows for successive decades of digital display of this incremental movement of the control plate 20 by the addition of porting associated with the bore 28, and additional ports 52 beyond those involved in the first cycle of successive port registration.

This porting includes an elongated slot 54 formed in the control plate 20 and a series of ports 56 formed in the housing 12 and extending into the bore 28. The spacing of the ports 56 and the distance the control plate 20 must move to register with the first or tenth port 56 from the zero position shown in FIG. 3 is set at the spacing of the ports 52 associated with the porting 50.

Thus as the valve plate 20 moves to the left, the piston 24 remains full up and a zero continues to appear in window 14 until the slot 54 reaches the position shown in FIG. 6 in which the first or tenth port 56 is uncovered. This occurs at the same point that the piston 26 returns to the zero point.

This causes the region in the bore 28 below the land 58 to be vented in similar fashion as with piston 26, also causing a pressure drop in this region, and a resulting pressure unbalance on the piston 26 causing it to move to the position shown in FIG. 6 to restrict this venting through the 10 port 56. In this position the numeral 1 appears in the window so that a 10 count is indicated. Continued movement of the control plate from the, position shown in FIG. 6 causes a repeat successive registration of the ports 50 with the ports series 52, as additional ports 52 are provided to the right as shown in this Figure, so that as the left most port 52 moves out of range of the port series 50, a series of nine ports 52 is still available for another cycle of the piston 26.

During this second cycle, the slot 54 continues to mg 7 ister with the 10 port of the port series 56 so that the numeral 1 continues to appear in the window 14.

After the piston 26 has again gone through its count cycle, the spacing of the slot 54 and port series 56 is such that with the last incremental movement of the control plate 20 which causes the piston 26 to return to zero, the second of the port series 20 comes into registry with the slot 54 causing the piston 28 to move to restrict this port, and causing the numeral 2 to appear in the window 14 to thus cause the count 20 to be indicated by the pistons 26 and 28.

In the application described above, it was indicated that a 60 count range would be adequate and thus in the embodiment shown five ports 56 are shown as well as four additional ports 52 to accommodate a count from 0-59.

From this description, it can be appreciated that a simple mechanical digital display has been provided which provides a digital count of increments of movement of an operator a tenth of that corresponding to a numeral change to thus make possible relatively high range counts with a reasonably compact structure.

Referring to FIGS. 7 and 8, an alternate embodiment is depicted featuring a rotating valve plate rather than the linear travel arrangement described above.

In this embodiment, a port series 60 and 62, equivalent to the porting series 50 and 56 of the abovedescribed embodiment are formed in partitions 64 and 66 communicating with a slot 68 formed in the housing 12, and are arranged along an are as shown in FIG. 8.

Disposed in the slot 68 is a rotary control plate 70 formed with a slot series 72 and a tee slot 74 corresponding to the earlier described porting series 52 and slot 54.

The rotary control plate 70 is coupled to the output mechanism (not shown) of a conventional bourdon tube 72 so that the rotary position of the rotary control plate 70 corresponds to the pressure sensed by the bourdon tube 72.

This pressure may be the pressure upstream of air gauge tooling 74 supplied with air under regulated pressure to sense the dimension of a port piece in the manner well known in the art.

This embodiment works in the same manner as the linear motion embodiment save the successive registrations occur as a result of angular movement of the rotary control plate 70 and venting occurs through the open ends of slots 72 into slot 68 and through the tee slot 74 to an internal cavity rather than directly through the valve plate.

Many other variations and applications of this invention are of course possible. For example, in a great many situations other than pressure sensing a need may arise for a digital readout of the position of movable member, and this device is thus not of course limited to use only in a pressure sensing context.

What is claimed is:

l. A mechanical motion device comprising:

a movable element;

a movable control member having a first series of control elements thereon;

a second series of control elements juxtaposed to said first series on a structure separate from said movable control member and said movable element and having a vernier spacing relationship with said first control element series on said movable control member;

means automatically shifting the position of said movable element in response to registrations of control elements in said first and second series of control elements, said registrations brought about by movement of said control member and said vernier relationship in their respective spacings, said movable element being shifted to positions corre sponding to the point of each of said registrations, where said shifting means is automatically disabled;

whereby movement of said movable element in response to said registrations is greater than the corresponding movement of said control member.

2. The device of claim 1 further including display means providing a display of the relative incremental position of the movable element and said separate structure corresponding to each of said positions corresponding to the point of said registrations.

3. The device of claim 2 wherein said display means comprises an ordered series of numerals on said movable element along the line of motion of said relative movement between said structure and said movable element, whereby a numerical display corresponding to movement of said control member is provided.

4. The device of claim 3 wherein the movement of said movable element is an order of magnitude greater than the movement of said control member in the number system of the numerals thereon and further includes:

a second movable element having an ordered series of numerals thereon, and means causing said second movable element to move together with movements of said control member in increments corresponding to that of said order of magnitude, whereby a numeral display corresponding to said control member movement of two successive orders of magnitude of said numeral system is provided.

5. The device of claim 4 wherein said numerals are decimal numbers whereby said movement of said movable element is ten times that of said control member.

6. The device of claim 4 further including means for returning said movable element to its initial position upon movement of said control member through a range of incremental movements corresponding tosaid control element registrations equal to the base of said numeral system.

7. The device of claim 6 wherein additional control elements are provided in one of said series than the number required to move said first movable element through a base number of increments whereby said range of incremental movements of said first movable element may be repeated upon continued movement of said control member.

8. The device of claim 4 wherein said means causing said second element to move includes a series of control elements on said separate structure and a control element on said movable member.

9. The device of claim 1 wherein said first and second series of control elements are series of ports formed therein and wherein said means shifting the position of said movable element includes means for applying fluid under pressure to said movable element and also includes means for controlling the application of fluid pressure to said movable element by the registration of ports in said first and second series of ports.

10. A fluid pressure mechanical movement display comprising:

a housing having a bore formed therein;

a movable element slidably disposed in said bore;

means for directing fluid under pressure to both sides of said movable element in said bore;

a series of ports formed in said bore wall;

control means including a movable control member having porting means associated therewith to provide venting of one side of said movable element through said ports in said port series at each of various incremental positions of said movable control element with respect to said housing;

said porting means including a series of ports in said control member, said series of ports in said bore wall are spaced in a vernier relationship to said porting means and further including means creating said venting by successive registrations of said ports in said port series in said bore wall and said control member. 

1. A mechanical motion device comprising: a movable element; a movable control member having a first series of control elements thereon; a second series of control elements juxtaposed to said first series on a structure separate from said movable control member and said movable element and having a vernier spacing relationship with said first control element series on said movable control member; means automatically shifting the position of said movable element in response to registrations of control elements in said first and second series of control elements, said registrations brought about by movement of said control member and said vernier relationship in their respective spacings, said movable element being shifted to positions corresponding to the point of each of said registrations, where said shifting means is automatically disabled; whereby movement of said movable element in response to said registrations is greater than the corresponding movement of said control member.
 2. The device of claim 1 further including display means providing a display of the relative incremental position of the movable element and said separate structure corresponding to each of said positions corresponding to the point of said registrations.
 3. The device of claim 2 wherein said display means comprises an ordered series of numerals on said movable element along the line of motion of said relative movement between said structure and said movable element, whereby a numerical display corresponding to movement of said control member is provided.
 4. The device of claim 3 wherein the movement of said movable element is an order of magnitude greater than the movement of said control member in tHe number system of the numerals thereon and further includes: a second movable element having an ordered series of numerals thereon, and means causing said second movable element to move together with movements of said control member in increments corresponding to that of said order of magnitude, whereby a numeral display corresponding to said control member movement of two successive orders of magnitude of said numeral system is provided.
 5. The device of claim 4 wherein said numerals are decimal numbers whereby said movement of said movable element is ten times that of said control member.
 6. The device of claim 4 further including means for returning said movable element to its initial position upon movement of said control member through a range of incremental movements corresponding to said control element registrations equal to the base of said numeral system.
 7. The device of claim 6 wherein additional control elements are provided in one of said series than the number required to move said first movable element through a base number of increments whereby said range of incremental movements of said first movable element may be repeated upon continued movement of said control member.
 8. The device of claim 4 wherein said means causing said second element to move includes a series of control elements on said separate structure and a control element on said movable member.
 9. The device of claim 1 wherein said first and second series of control elements are series of ports formed therein and wherein said means shifting the position of said movable element includes means for applying fluid under pressure to said movable element and also includes means for controlling the application of fluid pressure to said movable element by the registration of ports in said first and second series of ports.
 10. A fluid pressure mechanical movement display comprising: a housing having a bore formed therein; a movable element slidably disposed in said bore; means for directing fluid under pressure to both sides of said movable element in said bore; a series of ports formed in said bore wall; control means including a movable control member having porting means associated therewith to provide venting of one side of said movable element through said ports in said port series at each of various incremental positions of said movable control element with respect to said housing; said porting means including a series of ports in said control member, said series of ports in said bore wall are spaced in a vernier relationship to said porting means and further including means creating said venting by successive registrations of said ports in said port series in said bore wall and said control member. 